/* 计算模块（解决浮点数运算中出现的精度缺失问题） */

/**  
 * 加法
 * 
 * @param {Number|Float} arg1 参数1
 * @param {Number|Float} arg2 参数2
 */
function add(arg1, arg2) {
    var r1, r2, m, c;
    try {
        r1 = arg1.toString().split('.')[1].length;
    } catch (e) {
        r1 = 0;
    }
    try {
        r2 = arg2.toString().split('.')[1].length;
    } catch (e) {
        r2 = 0;
    }
    c = Math.abs(r1 - r2);
    m = Math.pow(10, Math.max(r1, r2));
    if (c > 0) {
        var cm = Math.pow(10, c);
        if (r1 > r2) {
            arg1 = Number(arg1.toString().replace('.', ''));
            arg2 = Number(arg2.toString().replace('.', '')) * cm;
        } else {
            arg1 = Number(arg1.toString().replace('.', '')) * cm;
            arg2 = Number(arg2.toString().replace('.', ''));
        }
    } else {
        arg1 = Number(arg1.toString().replace('.', ''));
        arg2 = Number(arg2.toString().replace('.', ''));
    }
    return (arg1 + arg2) / m;
}

/**  
 * 减法
 * 
 * @param {Number|Float} arg1 参数1
 * @param {Number|Float} arg2 参数2
 */
function sub(arg1, arg2) {
    var r1, r2, m, n;
    try {
        r1 = arg1.toString().split('.')[1].length;
    } catch (e) {
        r1 = 0;
    }
    try {
        r2 = arg2.toString().split('.')[1].length;
    } catch (e) {
        r2 = 0;
    }
    m = Math.pow(10, Math.max(r1, r2)); //last modify by deeka //动态控制精度长度
    n = (r1 >= r2) ? r1 : r2;
    return ((arg1 * m - arg2 * m) / m).toFixed(n);
}

/**  
 * 乘法
 * 
 * @param {Number|Float} arg1 参数1
 * @param {Number|Float} arg2 参数2
 */
function mul(arg1, arg2) {
    var m = 0,
        s1 = arg1.toString(),
        s2 = arg2.toString();
    try {
        m += s1.split('.')[1].length;
    } catch (e) {}
    try {
        m += s2.split('.')[1].length;
    } catch (e) {}
    return Number(s1.replace('.', '')) * Number(s2.replace('.', '')) / Math.pow(10, m);
}

/**
 * 除法
 * 
 * @param {Number|Float} arg1 参数1
 * @param {Number|Float} arg2 参数2
 */
function div(arg1, arg2) {
    var t1 = 0,
        t2 = 0,
        r1, r2;
    try {
        t1 = arg1.toString().split('.')[1].length;
    } catch (e) {}
    try {
        t2 = arg2.toString().split('.')[1].length;
    } catch (e) {}
    r1 = Number(arg1.toString().replace('.', ''));
    r2 = Number(arg2.toString().replace('.', ''));
    return (r1 / r2) * Math.pow(10, t2 - t1);
}

/**
 * 无条件舍去小数
 * 
 * @param {Number|Float} arg 参数
 * @param {Number} number 保留的小数点位数
 */
function rem(arg, number = null) {
    typeof arg != 'string' && (arg = arg.toString());
    let argArray = arg.split('.');
    if (number > 0) {
        if (argArray[1] && argArray[1].length > number) {

            argArray[1] = argArray[1].slice(0, number);
            arg = argArray[0] + '.' + argArray[1];
        }
    } else {
        arg = argArray[0];
    }
    return arg;
}

module.exports = {
    add,
    sub,
    mul,
    div,
    rem
}
